2004 Indmar Assault 5.7L Throttle/Bog Issue

[jzelt]

Since buying this boat a few years ago, our test ride went awesome (Pulled slalom skiers with no effort), but since then it hasn't ran the same way (spread out over 2 years time, but seems like forever since we used it every weekend for 8 months out of the year).

Our first issue was fuel filter. (Throttle would get lower and lower in RPM on takeoff. Eventually couldn't get above 3K RPM, then 2K, then could only idle).

Then it was idling high and puking black smoke out the exhaust. (Turned out to be throttle position sensor. Diagnosed by disconnecting the TPS cable and no
change in throttle reaction. Had to be steady on acceleration so you could get the right fuel to air ratio).
Took TPS off the intake and couldn't turn the innerds with my pinkie like I could with the new one. Real scientific I know. (seized)
Learning after replacing it and looking back, when I put the new one in, it had some spring tension, when I took the old one out, it wasn't under any
pressure/tension.

Then it was "electrical" by being a consistent hesitation around 2k RPM and couldn't hammer it down from idle or it would bog and die.
Steady throttle past 2K and then hammer down took off, but still a slow process pulling me out of the water more than it should have been.
If the driver was too anxious and put too much throttle in, it would start to pull and then bog and lots of time and energy wasted cause your attempt
was probably done that pull. (Me mostly driving, trying to get someone new to accomplish a watersport for the first time, I get over anxious and we
both get frustrated, me angry at the equipment and embarrassed).

Ruled out fuel flow issue by buying fuel gauge and constantly reading 32 PSI thru entire range. Still replaced fuel filter. Then in priming it, fuel pump
died (another $400), also blowing out the fuse (15 or 20 amp below the engine for anyone that has to find it).

Also, on return throttle to idle from running, would consistently idle high (1200 RPM). Pop the throttle and it would come back down 700 RPM. Cleaned
IAC thinking may be sticking, but it wasn't dirty to begin with. Kept thinking TPS because that was only thing I have changed before. Sprayed starter
fluid around gaskets thinking maybe air leak and computer was compensating. No changes.

Threw another $40 for TPS (thru autozone) and put it in on Fri night. Sat morning came, and told driver (wife) to hit me full throttle. We would either
both be extremely ecstatic or still scratching our head. For the first time in a long time, it pulled like a mule and ran for the reason we bought it.

So why this post? I am no mechanic. I try to save money by reading about issues and then following others suggestions. This site has been very helpful in direction for diagnosing, but I have seen plenty of posts with same motor, bog, hesitation, issue etc and several suggested tries, but no one ever posts what resolved it. As in my case, haven't they fixed it yet and just lived with it?

2 times it has been TPS related. Different issues both times. Keeping the hesitation one as a backup, but learned a ton thru the process.

Any additional info needed, I would be glad to elaborate more. Again, no mechanic, no scientific testing, just reasonable deduction on my part. Your experience may be different. Hoping that this post will help someone years down the road when they search for the same issue. Also hoping that others that had the issue read it and just forgot to update what their solution was... (Searched for parts for 1999 Chevy C1500 5.7 if it is a non-marine part).